(1) Field of the Invention
The present invention relates generally to measurements of line impedance and more particularly to a method and apparatus for accurately modeling a transmission line deployed in seawater for the purpose of determining amplitudes of received transmissions.
(2) Description of the Prior Art
Single wire transmission lines are used extensively by the United States Navy to communicate with underwater weapons launched from either surface ships or submarines. Typically, the transmission line (also known as a guidance wire) is coiled at each end such that one coiled end is maintained on the launching ship and the other coiled end is maintained within the weapon. Upon launching the weapon, the guidance wire is paid out from both the ship coil and the weapon coil. The paid out portion of the guidance wire is deployed in the seawater.
Guidance command (also known as command tone voltage values) consisting of a known voltage amplitude and frequency are sent from the ship to the weapon via the guidance wire. Responses by the weapon (also known as telcom tone voltage values) are then transmitted back to the ship via the guidance wire. Development of new combat systems and weapons required an accurate understanding of how the command and telcom tone voltage values are affected as more and more of the guidance wire is paid out. Accordingly, it is imperative that quantitative data be available for modeling of the guidance wire and payout coils in order to predict the amplitude of command and telcom tones being received. This will maximize design efficiency and eliminate the possibility that a marginal condition exists at a particular payout distance. Current methods of generating such data involve trial and error in an actual use environment. However, there is no current method of predicting the amplitude of a tone received for various payout lengths of cable, i.e., part of the length being coiled and part of the length being deployed in seawater.